Pour the batter into the cake tin and bake it in preheated oven for 25 to 27 minutes, until a toothpick inserted in the center of the cake comes out clean.
Prepare the chocolate sauce, mix the cacao, sugar, and salt in a bowl. Put ½ cup of water in a small saucepan and add the cacao mixture. Bring it to a boil, whisking occasionally.
To prepare the creme Chantilly, place the cold double cream or whipping cream, vanilla paste, and sugar in a bowl. Beat them until stiff and hold their shape nicely.